1960s Eico 955 In-Circuit Capacitor Tester Restoration and Overview

[@TheGuitologist]

NOTE: Several times in the video, I said the ESR (Equivalent Series Resistance) of a cap can be determined with this meter. There may still be a way to determine if a cap has high ESR with this meter, as it does provide a mechanism for calculating Power Factor, which is related to ESR, but not in the way I described. I sometimes get confused when conceptualizing ESR as it is not a measurement I deal with much when diagnosing cap problems old tube amps. Still, I should have been describing parallel resistance rather than series resistance, which is usually referred to as "leakage" or "shunt" resistance around a capacitor. Old caps usually just get replaced entirely or are sussed out because they have DC leakage (parallel resistance) which is causing issues. High ESR is rarely a problem we encounter practically in tube amps because tubes can still function even where a high ESR exists in most cases. Say a coupling capacitor has a leakage, or parallel resistance around it, allowing DC voltage to bypass the capacitive function of the component, maybe due to bad paper or moisture absorbed into the wax. This will cause a tube downstream to bias positive on the grid and either not function or worse, self-destruct. This is an easy problem to diagnose by placing a DMM on the capacitor and measure resistance, or by testing DC voltage at some point past the coupling cap such as the tube grid -- but if that same coupling cap has a high ESR, the amp may still function quite satisfactorily with almost completely negligible effects. In fact, it might even IMPROVE the tone of the amp in some way. the problems with high ESR come when the capacitor starts flowing a bunch of current through it because of a high ESR and with current flow comes heat in the form of Watts. So this can eventually be a problem too. The kind of equipment where ESR is a big concern is usually solid state equipment and/or equipment which is sensitive to certain resonant frequencies. THE FOLLOWING IS COPIED FROM ANTIQUERADIOS.COM FORUM: ""ESR and leakage testing are intended to catch two different kinds of problems. To test a capacitor fully, you need to do both. Look at it this way: if a capacitor is completely open, there will be no leakage so a leakage test will tell you it is perfect. On the other hand, an ESR test will show the impedance to be impossibly high. Should a capacitor be shorted or excessively leaky, an ESR test may well read perfect but a leakage test will surely flag it. One thing that needs to be understood is, the chemistry in many electrolytics changed around 1970. Prior to that, all electrolytes were water based. After 1970, glycol based electrolytes came into use for many kind of electrolytic caps. In any electrolytic capacitor, the electrolyte is gradually lost. Some of it is broken down by electrolysis and the oxygen is used to reform and maintain the aluminum oxide dielectric layer. Inevitably, some electrolyte is also lost due to evaporation through seals and end plugs. Now in a water based capacitor, when the electrolyte is no longer capable of replenishing the dielectric layer, it deforms and leakage current increases until the cap shorts out. In a glycol based capacitor, the electrolyte loses its ionic concentration and its ability to carry current is lost. It goes high in ESR and maybe becomes open. This is why you won't find any antique ESR testers, and they're not mentioned in old radio repair textbooks. Nobody needed them until more recently.""

[@sirbaronvoncount4147]

Brad your voice brings me back to a simpler time when things were different and people much kinder and gentler. I speak of the year 2019. How I miss those times.

[@alanparker2792]

Thanks

[@TheGuitologist]

Thank you Alan. Really appreciate all the support. You're amazing.

[@dagger21detroit58]

Thanks!

[@TheGuitologist]

No problem!

[@theadam2494]

I had an eico 14watt stereo amp that my dad built back in the fiftys from a kit . Great amp ! Wish I still had it .

[@kevinshea4776]

Brad, I really like when you do these videos on vintage equipment and educate us on how it works!

[@soapboxearth2]

Brad. TSP is an unbelievable cleaner. Painters use it to clean nicotine off of walls before painting. Great for cleaning old amp chassis etc.

[@oldelectronicsfan5136]

Actually, never mind. I just found the info I needed. For others who might need this here is what I found: The length of the test lead used is the sum of 42" RG-58A/U coaxial + 5" for the Red and Black cables which end in a cocodile clip each. Total length in centimeters: 106,68 cm RG-58A/U + 12,70 cm Red & Black cables = 119,38 cms. This length has to be exact since it is part of the tuned open test circuit (although a small error is permissible since the "Q" of the circuit is not critical), and represents a quarter wave-length line for the frequency of oscillation (about 22 Mcs).

[@TheGuitologist]

This is interesting then because in the video I'm using a gator clip to replace one lead which is too long. Thanks for bringing it to my attention.

[@oldelectronicsfan5136]

@@TheGuitologist You are welcome!

[@fiddlix]

I love old test equipment from the 50s-80s. Excellent informative video Brad. Keep up the excellent content. Thank you 🙏.

[@patprop74]

I have tons of them im willing to sell you haha

[@framusburns-hagstromiii808]

Cool piece of test gear! Eico made some good gear! Cheers!

[@EarslimeRecords619]

Brad posted ! Thank god

[@srtamplification]

Brad, according to the manual, the RC balance doesn't measure Equivalent Series Resistance (ESR). It measures Equivalent Shunt Resistance. Shunt is parallel. Another words in measures leakage. You want the ESR of a cap to be very low and the Shunt Resistance to be very high. The higher the ESR is, the more the cap is acting like a resistor. The higher the Shunt Resistance, the lower the DC leakage current.

[@salossi]

Almost correct. But still a mistake: A high ESR behaves like a cap and a resistor in series - and a leaking cap behaves like a cap and a resistor in parallel... So in case of usual caps in audio circuits, e.g. coupling caps etc, it's rather the leaking caps, that turn into resistors than the high ESR ones...

[@srtamplification]

​@@salossiMaybe you misunderstood what I said, but we're saying the same thing.

[@salossi]

@@srtamplification okay :)

[@TheGuitologist]

I think I correct myself at some point and say leakage. But yeah, that’s correct.

[@patprop74]

I have a Knight KG-680 Capacitor Checker, Like you said, i don't think it will ever be used as a Cap checker much, but the case and chasse could make for another interesting project such as a small tube amp head.

[@davidflamee]

Great old school bit of kit, and still bang on. The magic eye tube is provides a fascinating display for this purpose of testing capacitors. Ive only ever seen them used as recording level indicators and signal strength indicators in receivers. Very interesting video.

[@wesleymorris1]

I rebuilt one of these only mine is a Sprague cap tester.

[@alanparker2792]

Hello from England 🏴󠁧󠁢󠁥󠁮󠁧󠁿

[@thelightstillshines2476]

Nice video Brad keep up the good work!

[@pauldavis6356]

The capacitor tester needs new capacitors. The irony is classic ! Nicw video - keep 'em coming. 😀

[@vintageguitaramp_guitarteacher]

Great video Brad, thank you

[@shytweedabone2663]

Brilliant!

[@tedmich]

the 6FG6 EM85E CV5434 Magic Eye tube! People love these for old tuners (Macintosh notably)

[@rickashford4005]

Where the hell did you find that hypnotic sleep track. I couldn't stay awake to see all the video. I dreamed about suck starting a 12 ga shotgun!!! 😅😂🤣🤣

[@ToRung]

*_hello ❤😍🌹 have good day_*

[@oldelectronicsfan5136]

I just got one of these but it lacks the test lead.The manual says the cable is designed for this application and that you shouldn't substitute another cable. I am guessing that the length is one of the important parameters. The manual does say you can calibrate for a replacement cable. So, can you tell me the length of the one you have? It would give me a starting point at least.

[@TheGuitologist]

From the tip of the Amphenol connector to the tip of the gator clip is 49 inches. Hope that helps!

[@okayestguitar66]

Hayden amps, made some amps with the EM84 "eye" tubes in them, had a couple at one point. I have a nos EM84, RCA, I think, wasnt hard to get, nor was it expensive.

[@KingstownUkes]

love it

[@cantyouhearmeknocking1961]

I've got an old tube tester that still has the original cord. It's in really good shape, but I'm not plugging it up until I go over it good. Did you do a video on a tube tester? Heck, I can't remember. ;-)

[@Curtislow2]

I a guessing that "RC Balance" stands for resistance compensation balance.

[@P51ride]

If you find an EICO 950B RC bridge get it !!!. The 950B will allow testing of capacitor leakage with a DC voltage up to 500 VDC !!!!

[@spaguy007]

Hey brad buy a product called Plasti-Aid you can fill the hole redrill it and tap it for the set screw, its sets fast and can even be molded into many things. It will not breakout.

[@jamesbracken4618]

AMEN Brother, I'm glad to hear you say that. I watch you all the time. GOD BLESS YOU AND YOUR FAMILY! GOD BLESSS AMERICA!! GLORY BE TO GOD111 IN JESUS CHRIST NAME I PRAY!!!!!!!

[@nevillegoddard4966]

Hi Brad! Cool old school bit of test gear! I love those 'magic-eye' kinda signal indicators! Mate, as srt said, you really messed up thinking the ESR of that 4.7uF capacitor was 6.3k! If that was true the cap would be RUBBISH! If it's a new cap it's ESR would be more like 6.3 OHMS anyway! 😂! 'srt' read the manual, & the rc balance control adjusts for the SHUNT resistance, in fact. Then you said the ESR of the 100uF cap was almost infinite. Wrong again mate! It's ESR was ALMOST ZERO ohms! You seem a little confused Brad! Maybe read up on the difference between leakage & ESR. They are VERY different specs!

[@tankthelord1178]

Nice one Brad, I never lie as I am JC himself....... Happy New Year.

[@lroy730]

CA Glue is always my fisrt choice! That shit on everything ! 🐓

[@stepvanjoe3469]

Brad that tester would make a cool guitar amp head

[@roncarter2188]

Hey Brad where can I get the electrolytic lube? Most of the stuff I've found is really expensive and I know that ain't your style so why pay more than you need to! Thanks, great video.

[@drmlabs]

love that chill background music.

[@salossi]

And: An ESR of "around infinity" you'll get, if one of the leads of the cap is broken off 😉😂

[@archloy]

and what if we enjoy this but already subscribed ? x) Anyway, interesting. Also curious to see if it could be remake today easily

[@skullheadwater9839]

Weird, I thought 1022 was Mullard EIA code.

[@skullheadwater9839]

You and that damn hot glue, LOL.

[@TheGuitologist]

It works

[@mikeduino4596]

If that electrolytic is good,the esr will be very LOW. ESR IS NOT LEAKAGE!!!! ESR IS in series with the capacitance leakage is parallel to the capacitance, in other words a leaky cap is shorted. ESR is measured with an ESR meter which is an ohm meter that uses a 100khz test signal rather than the DC test current of a standard ohm meter.

[@tenlittleindians]

There's only 10-20 peecent alcohol in your WD-40 contact cleaner.

[@vanncooke934]

Please no more music in background. I love all of your videos but the music is killin me lol

[@salossi]

ESR of 6,3k ohms with a new cap??? :) Nope, that was definitely a mistake!! It's not ESR, what you are measuring here.

[@GlennSpitzer-mi4cl]

I never felt comfortable with tube and capacitor testers, where you go ok that's what it says. You will be fooled. You have too know yours from experience and develop a sense. Because high current is involved. It's like testing a bullet proof vest with a pee shooter. lol You can tell by DC and swapping tubes. Otherwise it's like asking a Witch. I never was on a bench troubleshooting with one of these things. an experienced tech would come up and say get rid of that thing.

[@christopher-s7w]

i have a pet turtle...

[@williambaker1136]

😂"Jesus Christ and liars" ....i will steal that one

[@MrMac5150]

Cut your finger nails. please.

[@nevillegoddard4966]

@@MrMac5150 He won't do that mate. He has his own picking style with guitars, where he uses his fingernails as actual 'picks'. Now if they were dirty, that would be a different story!

[@MrMac5150]

@@nevillegoddard4966 Just a disgusting excuse. Next you will say its okay to have brown nails from picking your a s s

[@brich2929]

I don't like your narrated videos

[@PennStacker]

Thanks!

[@TheGuitologist]

Welcome!